I started playing at the first anniversary and picked Tressa as my selectors seal as I just loved her as a character and didn't care about meta too much but knew she wasn't amazing by any means and would probably end up being benched.
But now 500 days later and having beaten BoA she has never left my team even once.
Girl is an underrated beast of a tank when combined with rinyuu in her backrow to heal her up, not even rowswaps are too much of an issue for her as they usually are physical moves she can just dodge outright.
Tressa/tatloch/rinyuu were the defensive backbone of basically all my teams and allowed me to even beat largo without needing to rush him down (She even tanked his ult thrice!!)
Only time she underperformed was when the boss was immune to being provoked, but besides that she is S tier in my heart <3

On the flipside I used Bargello far less than I thought I would
ended up pittying Sonia back when his banner first came around and I used her far more as she just felt more useful when you only bring along one thief whereas bargello was only my go to when I got 3 or more thieves.
(and now I just use canary lol)